Alternatives to current human adjuvants are needed. Our studies demonstrate that in the absence of adjuvant, targeting antigen (Ag) to human Fcgamma receptor type I (hFcgammaRI) on Ag presenting cells enhances T cell activation in vitro and Ag-specific antibody (Ab) and cytokine production in vivo. However, no one has created recombinant immunogens, which permit examination of the hFcgammaRI targeting approach in an infectious disease model, or the deliberate study of the mechanism(s) involved. Strepto- coccus pneumoniae is a respiratory pathogen for which a protective Ag (PspA) has been identified. PspA is a bacterial surface protein, which, when used as an immunogen with adjuvant, generates protection against S. pneumoniae infection in mice. We hypothesize: 1) That protection against S. pneumoniae infection can be enhanced (in the absence of adjuvant) by immunizing with an anti-hFcgammaRI-PspA fusion protein. 2) That the mechanism(s) of enhancement will involve alterations in Ag localization to lymphoid tissues, as well as alterations in Ag processing. To test the latter, we will generate an anti-hFcgammaRI-HEL fusion protein. HEL is a protein Ag commonly used to conduct mechanistic studies of Ag processing and presentation, in vitro and in vivo. In Speific Aim 1 we will: A) Dehumanize anti-hFcgammaRI-PspA and anti-hFcgammaRI- HEL fusion proteins already generated. B) Examine the ability of the fusion proteins to enhance T and B cell responses in vitro and in vivo. C) Determine, in vivo, if hFcgammaRI targeting of Ag works, in part, through enhanced localization of Ag to lymphoid tissues. In Specific Aim 2 we will: A) Test the ability of the anti- hFcgammaRI-PspA fusion protein to protect against challenge with S. pneumoniae. B) Study the influence of hFcgammaRI targeting on Ag processing and presentation utilizing biochemical, immunological and ultrastructural techniques. The proposed studies will lay the ground-work for further hFcgammaRI targeting studies using a variety of infectious disease agents in mouse and human, eliminate the need for traditional adjuvant, substantially reduce the amount of Ag required to vaccinate an individual (reducing cost and potential toxicity), and provide a vaccine delivery system, which simultaneously enhances humoral and cellular immune responses. Thus, these studies and this vaccine strategy will be applicable to vaccines against a wide variety of pathogens in adult, pediatric, and immunocompromised populations.